The invention relates to a method for producing inner and/or outer contours deviating from a circular shape on a machine with clamping of at least one workpiece that is rotatably driven at a constant speed and of at least one tool, especially for machining by cutting, wherein the tool is moveable by a carriage radially to the rotational axis of the workpiece as well as axially in the longitudinal direction of this rotational axis. Furthermore, the invention relates to a device for performing this method.
A method for producing workpieces with polygonal outer and/or inner contours by a cutting machining process is known from European patent 0 097 346. In this known method, the workpiece guided on a circular path engages during the entire revolution at a workpiece whereby the path velocity of the tool is respectively changed during each revolution according to a periodic movement law. This permanent change of the path velocity of the tool during each revolution requires, in addition to programmable functional transmitters for the tool drive, a transmission that is controlled according to Pascal curves. Accordingly, this known method allows the manufacture of a plurality of polygonal outer and inner contours. However, because of the permanent control of the path velocity of the tool it requires a great control-technological and machine-related expenditure so that this method can be performed only on devices that are specially designed for this method and have controllable transmissions for the tool drive.
It is an object of the invention to provide a method for producing inner and/or outer contours deviating from a circular shape with which inner and/or outer contours deviating from a circular shape can be produced as desired with minimal control-technological expenditure and with commercially available devices. Furthermore, the invention has the object to provide a device for preforming this method.
The solution of this object in regard to the method is inventively characterized by the tool with its effective surface being rotatably driven about a tool axis on a circular path with constant velocity that deviates from the revolutions per minute of the workpiece with respect to size and/or direction of rotation, whereby the tool axis is different from the rotational axis of the workpiece.
Due to the different velocities and optionally different rotational directions of the constantly rotating workpiece, on the one hand, as well as due to the different rotational centers and the selectable radius of the circular movement path of the effective tool surface, a plurality of contours of movement paths of the effective tool surface resulting from the afore-mentioned parameters are produced. The special advantage of this method is that, despite the constant rotational velocities of the workpiece and of the tool, different contours deviating from the circular shape can be produced and that, on the other hand, this method can be performed on conventional devices because for driving the tool mounted on a carriage only a separate drive but no complicated controllable transmission for coupling the rotary velocities between tool and workpiece is necessary. The contour of the contour that deviates from the circular geometry is thus only dependent on the respective constant ratio of the revolutions per minute of the axes of rotation, the radius of the outer circle described by the tool as well as the axial offset of the axes of rotation.
According to a preferred embodiment of the inventive method the difference of the revolutions per minute between the workpiece, on the one hand, and the tool, on the other hand, is an integer. The revolutions per minute differences in integers will result, for example, for a ratio of 2:1 in triangular and for a ratio of 3:1 in quadrangular contours.
In an alternative embodiment of the inventive method the plurality of contours to be produced can be further increased such that the tool axis itself is driven on a circular path with constant velocity that deviates with regard to size and/or rotational direction from the revolutions per minute of the tool about an eccentric axis which deviates from the tool axis.
The three possible axes of rotation, i.e., the tool axis, the workpiece axis, as well as the eccentric axis, extend parallel to one another according to one embodiment of the invention. The parallel extending axes of rotation result in a straight inner and/or outer contour of the workpiece, i.e., a contour parallel to the axis of the workpiece.
According to a further embodiment of the invention, the position of the rotational axes relative to one another can be individually adjusted. By adjusting the position of the axes of rotation, the so-called phase angle, screw-shaped outer and/or inner counters can be produced.
For changing the diameter of the contour deviating from the circular geometry as well as for producing conical and spherical contours it is suggested, in a further development of the invention, that the radius of the outer circle described by the tool can be continuously adjusted by a cross-slide rest rotating with the axis of rotation of the tool and arranged on the tool spindle.
The solution to the object with regard to the device is characterized in that the tool, on the one hand, is clamped on a tool spindle and is rotatably driven on a circular path with constant velocity that deviates from the revolutions per minute of the workpiece with regard to size and/or rotational direction about a tool axis which is different from the rotational axis of the workpiece.
Finally, it is suggested with the invention that the tool axis is arranged eccentric to the tool spindle and is driven on a circular path with constant velocity, that deviates from the revolutions per minute of the tool with regard to size and/or direction of rotation, about an eccentric axis which is different from the tool axis. This additional axis of rotation allows the manufacture of a plurality of new inner and/or outer counters deviating from the circular shape. Especially, the manufacture of individual depressions within the workpiece wall or even penetrations of the workpiece wall can be provided with this inventive design of the device.